Hollygrove drainage to be reassessed

Responding to the long-standing concerns of Hollygrove residents that upcoming efforts to increase drainage capacity across Uptown New Orleans will exacerbate flooding in their area, the Army Corps of Engineers and the Sewerage & Water Board this week will launch a new round of hydraulic computer modeling to reassess the work's effect on the neighborhood.

View full sizeEliot Kamenitz, The Times-PicayuneContractors with the Corps of Engineers are planting 370 crape myrtles and willow oak trees by the end of next month along the half-mile stretch of Napoleon Avenue and on South Claiborne Avenue between Nashville and Louisiana streets.

Since Hurricane Katrina, Hollygrove denizens have posited that water flowing west from Uptown backs up water already in the Monticello Canal, which runs along the western edge of their neighborhood at the Jefferson Parish line. The Monticello Canal empties into the wider 17th Street Canal, then into Lake Pontchartrain.

With contracts slated to be awarded beginning this year to expand underground drainage capacity along Napoleon, South Claiborne, Jefferson and Louisiana avenues -- which all empty into the 17th Street Canal through various waterways -- Hollygrove residents fear flooding along in their neighborhood will worsen.

Stan Green, a senior project manager for the Southeast Louisiana Urban Flood Control project, or SELA, said it's unlikely that water entering the 17th Street Canal at the Palmetto Canal on the northern edge of Hollygrove would impede flow in the Monticello Canal.

He cited the mammoth capacity of Pump Station No. 6, which straddles the 17th Street Canal about a mile south of the lake, to siphon water out of the waterway.

However, Green pointed to a section of the Monticello Canal where the culvert narrows as it passes under Airline Drive and an adjacent railroad track. The bottleneck, about three-fifths of a mile north of the canal's origin at South Claiborne Avenue, could force water to back up into the large section of the Monticello Canal south of Airline Drive, he said.

A corps analysis conducted years ago found that the flow of water through the Monticello Canal would not be impeded by the pending Uptown projects, which aim to accelerate the flow of water off city streets and into the 17th Street Canal, Green said.

"Prior analysis showed there would not be any problem for a 10-year event," he said. "But because so many concerns have been expressed by residents," officials with the corps and the S&WB have agreed to review their hydraulic models and produce a fresh report on the effects of the proposed work. The agencies share the cost and oversight of SELA projects.

Green said the results will take three or four months to generate.

Whatever the conclusion, the corps' findings will not affect the timeline for drainage improvements along South Claiborne Avenue, for which the first contract is slated to be awarded in January, S&WB spokesman Robert Jackson said.

The water board's modeling to date has mirrored the corps' findings that "the additional Uptown SELA projects would not create a flooding situation during a 10-year design storm in the Hollygrove area," he said.

That said, the corps has rejected water board requests for reconstruction of the Monticello Canal, including expanding and deepening the waterway and erecting floodwalls as part of the SELA program, Jackson said.

The project has not met cost-benefit standards that the engineering agency uses to gauge SELA projects, he said, adding that if the new hydraulic study produces different results, that scenario might change.

Meanwhile, the corps is on track to award by late this year a contract for the second phase of its massive effort to improve drainage along Napoleon Avenue. The project began before Katrina with a $22.6 million effort to build a 19 foot-by-13 foot covered, concrete canal beneath the Napoleon Avenue neutral ground between Broad Street and South Claiborne Avenue.

The job finally is getting its finishing touches as corps contractors work to plant 370 crape myrtles and willow oak trees by the end of next month along the half-mile stretch of Napoleon Avenue and on South Claiborne Avenue between Nashville and Louisiana streets, SELA project manager Lori Wingate said.

Also under construction is a 3,100-foot path that will wind along the Napoleon Avenue neutral ground. Together, the work costs $620,000.

Other work to expand drainage capacity along the four Uptown thoroughfares is slated to be awarded through spring 2012, with completion of all jobs by summer 2016.